Outlier Detected? Here’s What It Means and What to Do

Outlier results may occur during soil analysis when a sample significantly differs from expected values. This can be caused by soil characteristics, sampling conditions, or preparation issues.

Five Common Causes of Outliers

1. High mineral content

   • Examples: peat soils, volcanic soils, presence of ash in the soil

      

2. Sampling depth

   • Samples taken deeper than 30 cm may fall outside calibration range

      

3. Very sandy soils

   • Example: beach sand

      

4. High organic matter content

   • Example: soils collected from forests or nearby areas

      

5. Improper sample preparation

   • Soil not fully dried

   • Presence of moisture during analysis

What to Do

Follow these steps to resolve or verify the outlier:

1. Repeat Sample Preparation

• Dry the soil again at 40°C
• Grind and mill properly before re-analysis, ensure the sample is completely dry

2. Check Sample Origin

• Confirm where the soil was collected
• Identify if the area is outside calibrated regions, volcanic or otherwise unusual as these can be an issue

3. Review Farm Management Practices

• Check if there has been recent applications of:
  • Manure
  • Compost
  • Lime
  • Fertilizers

These can temporarily affect soil composition and results.